Streptococcus Pyogenes Flashcards by Mandeep Chandi

What is the major VF of Strep Pyogenes?

M protein

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Characteristic of Strep. Pyogenes?

GABHS (group A beta hemolytic streptococci)
Gram positive cocci chain
major cause of cellulitis

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Strep Pyogenes is most common cause of what?

Bacterial cause of sore throat and immune mediated complications

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Transmission of Strep Pyogenes?

Person-to-person spread by respiratory droplets (pharyngitis) or through breaks in the skin after direct contact, fomite, or arthropod vector

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What does the VF Hyaluronic acid capsule do?

produces C5a peptidase

- interferes with phagcytosis

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What is the function of M protein?

hair like projections on CW which promotes adherence. Antiphagocytic and Anticomplement

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What things are associated with Adherence and invasion into host cells?

Lipoteichoic acid, M protein, and F protein

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Streptococcal Pyrogenic Exotoxins (erythrogenic toxin) are produced by?

Lysogenic strains of streptococci

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Strep Pyrogenic Exotoxin acts as what and interacts with whom?

SPE acts as a superantigen and interacts with both macrophages and helper T cells.

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Strep Pyrogenic Exotoxin is responsible for what?

Necrotizing fasciitis and streptococcal toxic shock syndrome as well as rash observed in patients with Scarlet Fever

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Streptolysin S?

O2 stable –> non-immunogenic and responsible for the hemolysis in Blood agar

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Streptolysin O?

O2 labile –> lyses WBC, platelets, RBC and mammalian cells. Immunogenic

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what is the treatment of coronary artery disease and venous thromboses?

Streptokinase (fibrinolysin)

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What is an important marker of S. pyogenes infection?

Antibodies against DNAse B

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What are the Suppurative infections?

Phayngitis
Scarlet fever
Pyoderma
Erysipelas
Cellulitis
Necrotizing fasciitis
Strep toxic shock syndrome

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What are the non-suppurative complications/sequelae?

Acute rheumatic fever

2. Acute glomerulonephritis

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Pharyngitis or ‘Strep Throat’ clinical features are?

Petachiae, Inflamed LN, Purulent exudate

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Other signs of Pharyngitis ‘Strep throat’?

swollen “strawberry tongue”

- soft palate shows petachie

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Scarlet fever is a complication of what?

Complication of pharyngitis due to pyrogenic toxin

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Clinical manifestation of Scarlet fever RASH?

diffuse erythematous/sandpaper like rash on the upper chest and then spreads to the extremities with sparing of the mouth, palms and soles

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Scarlet Fever clinical features?

Strawberry tongue
Pastia lines
Circumoral pallor (sparring of mouth)
Sandpaper wash

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Impetigo effects what part of skin and soft tissue?

Epidermis

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Erysipelas and Cellulitis effects what part of skin and soft tissue?

Dermis

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Necrotizing fasciitis effects what part of skin and soft tissue?

Hypodermis

What is Pyoderma/Impetigo?

Localized purulent streptococcal infection of skin that primarily effects exposed areas.

What is the progression of pyoderma/impetigo?

Papule --> Vesicle --> Pustule --> Thick crust

The fluid in blisters for Pyoderma/impetigo is...?

Serous or "honey colored"

What is Erysipelas?

Acute inflammation of skin with lymphatic involvement. Often involves face, trunk and extremities following pharyngitis.

Patients with Erysipelas usually experience what?

localized pain, inflammation, LM enlargement, and systemic signs.

how do you distinguish cellulitis infected skin from non infected skin?

CAN NOT BE DISTINGUISHED it is not clear.

What is Necrotizing fasciitis?

Streptococcal Gangrene

Necrotizing fasciitis is caused by what factors of Strep pyogenes?

Hyaluronidase, M protein, and Hemolysin O and S

Currently Strep. Pyogenes is most frequent agent of Necrotizing fasciitis. But what other organisms may cause this?

- C. Perfringens | - S. Aureus

How does Streptococcal Toxic Shock Syndrome (STTS) occur?

S. pyogenes grows in wound --> GABHS enters blood stream, and produce superantigen --> Fever, rash, shock, etc

compared to STTS, how does TSS occur?

S. aureus grows in tampon or wound --> TSST-1 toxin enters bloodstream (no bacteremia) --> Fever, rash, shock.

What are other infections of Strep pyogenes?

1. Puerpural Sepsis "childbed fever" 2. Acute Endocarditis 3. Pneumonia

What M types are rheumatogenic in Acute Rheumatic Fever (ARF)?

M6 and M12

Acute Rheumatic Fever is due to...?

cross-reactions between antigens of the heart and joint tissues, and the streptococcal antigen

Acute Post-Streptococcal Glomerulonephritis characteristics?

- Follows Skin or Throat infections - Presumptive: Dark urine (hematuria) - Definitive

Acute Post-Streptococcal Glomerulonephritis Key finding?

Loss of bowman's space, choking or vessel lumen

Importance of Microscopic examination of smears?

Gram +ve cocci in chains seen in the pus are important, but in throat swab it is not important.

What is the selective medium for Strep. pyogenes?

Crystal Violet Blood Agar

When you do a culture on blood agar what do you see?

Small, circular, colonies with wide zone of B haemolysis.

Catalase test for Streptococci would show what result?

Negative

PYR test (pyrrolidonyl naphthalamide) would yield what result for Strep pyogenes?

Positive for Strep. Pyogenes BUT, negative for other streptococci

Bacitracin sensitivity would yield what result for Strep pyogenes?

Positive for Strep pyogenes BUT, negative for other streptococci

Serological test would provide what?

evidence for prior streptococcal infection as Abs appear after 3-4 weeks.

What is are some examples of a serological test for Streptococci?

- Antistreptolysin O (ASO) test (neutralisation test) - Antigen Detection Test - Rapid Latex Antigen Kit

What is Antigen detection test used for?

its a agglutination test used to see group A streptococcal antigen from throat swab.

What is the treatment for Strep Pyogenes?

Penicillin is drug of choice. - starting therapy within 10 days prevents rheumatic fever - no treatment for glomerulonephritis

Children 5-15 years old can get what with s. pneumoniae?

Pharyngitis

Children ages 2-5 with poor personal hygiene can get what from s. pneumoniae?

Pyoderma

What is useful for documenting recent group A streptococcal infections?

Anti-ASO test

What is the criteria to diagnose rheumatic fever?

"JONES" - Joints: polyarthritis - Carditis - Nodules (subcutaneous) - Erythema marginatum - Syndenham's chorea

Pharyngitis can result in what?

rheumatic fever and glomerulonephritis

Impetigo more commonly precedes what?

glomerulonephritis more than pharyngitis

ASO titer detects recent infection with what?

S. pyogenes

Strep Pyogenes causes? (Pyogenic, Toxogenic, Immunogenic)

Pyogenic: pharyngitis, cellulitis, impetigo Toxogenic: scarlet fever, toxic-shock like syndrome, necrotizing fasciitis Immunogenic: rheumatoid arthritis, acute glomerulonephritis